1. Field of the Invention
The present invention relates generally to an ultrasonic cutting device and, more particularly, relates to a surgical cutting device with vessel-grasping jaws and an extendable blade-shaped ultrasonic cutting and cauterizing waveguide.
2. Description of the Related Art
Ultrasonic instruments are effectively used in the treatment of many medical conditions. Cutting instruments that utilize ultrasonic waves employ an ultrasonic transducer to generate vibrations along a longitudinal axis of a cutting blade. By placing a resonant wave along the length of the blade, high-speed longitudinal mechanical movement is produced at the blade's end. These instruments are advantageous because the mechanical vibrations transmitted to the end of the blade are very effective at cutting organic tissue and, simultaneously, at generating heat sufficient to cauterize the tissue. Such instruments are particularly well suited for use in minimally invasive procedures, such as endoscopic or laparoscopic procedures, where the blade is passed through a trocar to reach the surgical site.
Physical limitations of known materials used for ultrasonic generators and waveguides limit the speed and size of waveforms used to produce the ultrasonic movement. These limitations define a finite length at the end of the waveguide, referred to as a “hot spot,” that can effectively be used to perform the cutting and hemostasis. Tissue touching the waveguide at a particular distance away from the end of the waveguide (outside the hot spot) may be cut, but will not receive enough movement energy to generate the necessary heat to cause hemostasis. When performing endoscopic or laparoscopic surgery, hemostasis is critical because, where the bleeding is not kept under control, the non-invasive laparoscopy must be abandoned and the patient's body cut open to perform surgery on the otherwise inaccessible bleeding area.
Vessels are of particular import when performing ultrasonic surgery. Once severed, a vessel must be properly sealed to prevent dangerous high-volume blood loss by the patient. Vessels of smaller diameters are able to fall entirely within the hot spot of an ultrasonic cutting blade, resulting in a precise cut and complete sealing of the two open ends of the newly cut vessel. However, larger vessels, such as those with a diameter greater than 7 mm, exceed the width of the hotspot at the end of prior-art blades. This is especially true when the vessel is clamped and flattens out to around 11 mm.
Several devices exist that allow for simultaneous or substantially simultaneous cutting and sealing of large-diameter vessels. One such device 100, shown in FIG. 1, for example, is a bipolar electrocautery vessel sealer that has jaws 102, 104 which clamp across the vessel to be sealed. The clamping approximates the opposing walls of the vessel closely, providing a coaptive force. An open slot 106 runs down the middle of the jaws 102, 104 allowing a knife 108 to translate from the proximal end 110 of the jaws 102, 104 to the distal end 112 of the jaws 102, 104. The sealing process is as follows: The jaws 102, 104 are clamped across the vessel to be sealed. Bipolar (each of the jaws is a pole) electrocautery energy is applied to the clamped area of tissue. The energy heats and cauterizes the tissue causing it to become sealed together through the coaptive clamping forces of the jaws. Once the energy has been applied, the knife 108 is translated through the slot 106 in the middle of the jaws 102, 104 thus dividing the sealed vessel in the middle of the sealed area.
Another prior-art device for cutting tissue with an ultrasonic cutting blade is shown in FIG. 2. The ultrasonic clamping and cutting device 200 utilizes a clamp 202 having a set of jaws 204, 206 to clamp tissue in a particular area. Once the tissue is compressed to the point that blood can no longer flow into the clamped areas (i.e., hemostasis), ultrasonic movement is applied through a shaft 212 to an ultrasonic cutting blade 208. The blade moves relative to the jaws 204, 206 to pass through the clamped tissue. High-speed “sawing” movement of the blade 208 immediately slices through the tissue. The friction of the high-speed blade 208 is intended to also create frictional heat, which heat causes the tissue on either side of the cut to cauterize.
However, the prior-art instrument shown in FIG. 2 has a significant gap 210 around the cutting blade 208. The gap 210 is necessary in this device to allow the moving blade 208 to slide between the jaws 206. If this device were used on a vessel, it would not provide coaptive forces to opposing walls of the vessel as it translates and cuts. Close coaption of tissue while the ultrasonic energy is applied is critical when sealing a vessel using ultrasonic energy. Without this coaptive force holding the opposing walls of the vessel tightly together during the application of the ultrasonic energy, the opposing walls of the vessel will not seal together. Once the blade 208 cuts through the vessel, the gap 210 allows the vessel to pull away from the blade 208, often before the vessel is heated by the blade 208 and properly sealed. Naturally, as the diameter of the vessel being cut increases, this hemostasis problem is exacerbated.
Therefore, a need exists to overcome the problems associated with the prior art, for example, those discussed above.